Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, openWorldHint=false, so the safety profile is fully covered without the description. The description adds that this is a static reference/taxonomy lookup and discloses a 5-credit cost, which is genuine but modest added context; no behavior beyond that (result volume, pagination of the directory) is described.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short sentences lead with the resource and its tag set, followed by the taxonomy note, and the group/cost metadata is compact. Nothing is padded, though the tag enumeration is a bare list rather than a tightening of purpose.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return-value detail is not required, and for a read-only static directory the description plus schema and annotations are nearly sufficient. The one real gap is that a reader cannot tell from this text alone why they would pick it over the by_chakra/by_zodiac/by_purpose variants.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so both 'fields' and 'precision' are documented in the schema and the baseline is 3. The description adds nothing about the compact-mode projection or decimal rounding, and notably the schema's example paths (planets.longitude, houses.cusp) are unrelated to the crystal domain the description enumerates.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a concrete resource with its tag dimensions ('Reference list of crystals with chakra, zodiac, planet, element, hardness, and purpose tags'), so an agent knows exactly what it gets. It does not, however, name or distinguish itself from the filtered siblings (crystals_by_chakra_chakra, crystals_by_zodiac_sign, crystals_recommend) that cover overlapping ground.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no explicit when-to-use or when-not statement, and no sibling is named as an alternative despite four closely related crystal tools existing. The clause 'Returns chakra and purpose taxonomies for filtering' only implies that this is the discovery step before the by_chakra/by_purpose tools, leaving the routing to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.